In order to determine the sequence of the entire transcript, RT-PCR using primers in exons 10 and 11 paired with a primer in intron 12 was performed using BALB/c mouse brain total RNA and the resulting products sequenced. These products show that the larger transcript is due to an alternative splice event that results in an expanded exon 13. Specifically, exon 12 splices at bp 436 of intron 12, creating a large 1614 bp exon 13 that splices correctly to exon 14. The open reading frame of this alternatively spliced transcript is 611 amino acids, 28 amino acids longer than the message encoded by the 2.4 kb transcript.